It is important to monitor a pacemaker during its life to determine how the pacemaker is functioning including its operating parameters as well as determining the end of its battery's life. Through telephonic monitoring, typically using a small, portable monitoring device and a telephone, a patient can remain at home while the doctor or physician can still obtain this information. A signal corresponding to the pacemaker output is produced by the remote monitoring device, then sent through the telephone lines to a receiving center located at a hospital, clinic or doctor's office. This signal can then be read by a qualified person to determine the necessary information about the pacemaker such as its pulse rate, pulse width and magnetic rate. The present pulse rate of the pacemaker can be compared to the original pulse rate at implant or to a subsequently programmed pulse rate. Any deviation in the pacemaker pulse rate could indicate a potential problem with the pacemaker and appropriate corrective measures can be taken by the physician. Similarly, the pacemaker pulse width can be telephonically monitored and compared to the original pulse width of the pacemaker at implant or to a programmed pulse width. The magnetic rate of the pacemaker can be measured by placing a magnet on the patient's chest over the pacemaker implant location causing the pacemaker to operate in a magnetic rate mode. In many pacemakers the magnetic rate is used to determine battery life by calculating the percentage increase or decrease in the magnetic rate. Since magnetic rate fluctuation is gradual, telephonic monitoring, permits early detection of premature battery depletion, and steps for replacement can be made to provide maximum patient safety.
Patients with implanted pacemakers are typically monitored over the telephone using the following procedure. The patient is given a small, portable telephonic monitoring device, typically about the size of a transistor radio. This monitor is used to transmit vital pacemaker signals by telephone to a receiving center. By sending a beeping tone from the monitor over the telephone lines, pacemaker parameters such as pulse rate, pulse width and magnetic rate, can be determined by the physician or clinician at the receiving center who is able to confirm that the pacemaker is functioning properly. A receiving center typically consists of an EKG processing module, a phone boot for the receiving center telephone, and a built-in thermal printer for operator analysis of an EKG strip chart which shows the pacemaker functioning.
Current pacemaker monitoring devices are shown and described in U.S. Pat. Nos. 4,622,979 and 3,885,552, as well as in the operating instructions for a device manufactured by Instromedix.RTM. of Hillsboro, Oreg. called the Pacer-Tracer.RTM.. In order for the patient to operate these monitors, electrodes are needed to transmit the desired signals from the pacemaker to the monitoring devices. There are three basic types of electrodes currently being used, namely fingertip electrodes, wrist electrodes and chest electrodes. Fingertip electrodes are usually conductive pads that wrap around the tips of the index fingers. These pads are connected to wires which plug into jacks in the monitor. Wrist electrodes are similar to fingertip electrodes but are placed on both wrists and are usually made of conductive material attached to a flexible and expandable wristband. In the chest electrode monitor, the four chest electrodes can actually be part of the monitor and act as "feet" on the bottom of the unit. The monitor is placed over the patient's chest with the four electrode feet making contact with the patient's skin to transmit the signal. All three of the current methods of electrode placement, however, are inconvenient for elderly patients to use, especially when one considers that they must first speak over the telephone and second place the telephone handset over the monitor without dislodging the electrodes which may be located on either their fingers, wrists or chest.
The inconvenience of these electrodes is compounded when the magnetic rate of the pacemaker is transmitted. To have the pacemaker operate in the magnetic mode, a magnet must also be placed on the patient's chest, over the pacemaker location. This is not easily accomplished when the patient is also trying to place the telephone receiver over the monitor to transmit the pacemaker signals while not dislodging the electrodes from either their fingers, wrists or chest. Also, it is important to keep the magnet fairly still and positioned over the pacemaker to obtain an accurate reading of the magnetic mode.
Another disadvantage with the current monitoring devices is that there is no convenient way for the patient to know whether the pacemaker signals are being transmitted properly. This can be frustrating not only to the patient, but also to the operator or clinician reading the signals at the receiving center. One method currently being used is for the operator to observe a faulty or improper set of signals and to push a patient alert button at the receiving center which sends a loud buzzing sound over the telephone line. This sound emanates from the telephone handset or receiver and is supposed to notify the patient that the is to pickup the handset. Several problems exist, however, with this audio patient alert system. For example, the patient usually has the telephone handset over the monitor and cannot hear the loud buzz from the handset. Also, since most patients are elderly, hearing the buzzing sound is often a problem.
It would be desirable, therefore, to have a telephonic pacemaker monitoring device which did not have the above-described disadvantages and which could also function as a single channel EKG.